Knock-down shelving systems have been known for a great many years. Many of these, such as the systems disclosed in the patents to Flora et al. U.S. Pat. No. 2,596,332, Rasmussen U.S. Pat. No. 3,042,221, Miller U.S. Pat. No. 3,465,895, Jarvis U.S. Pat. No. 3,858,996, Bachand U.S. Pat. No. 4,161,303 and Ruschitzka U.S. Pat. No. 4,379,430, have required the use of special clips, retainers, latches, bolts or other such fasteners to hold the shelves in their erected condition. However, other shelving systems, some of which have been known for 50 years or more, have not required the use of such fasteners. Examples of these systems are those disclosed in the patents to Gibson et al. U.S. Pat. No. 1,984,473, Jackson et al. U.S. Pat. No. 2,266,206, Orlandi U.S. Pat. No. 3,850,396 and Markham U.S. Pat. No. 3,965,826.
Some prior art shelf hangers or brackets have reflected the desirability of maintaining the shelf in substantially the same orientation with respect to the horizontal while the shelf is being connected to, or disconnected from, the upright posts of the shelving system when the vertical positioning of the shelf is being adjusted. However, none of the prior art systems, so far as applicant is aware, have achieved this desirable feature as simply, and with the same degree of security, as does the present invention. As examples, both applicant's own U.S. Pat. No. 3,850,396 and Markham U.S. Pat. No. 3,965,826 involve more complicated structures than the present invention, and neither achieves the same security as this invention does.